石油污染土壤植物修复技术研究及展望

石油在开采、运输和炼制过程中,由于操作不当等原因,常会有泄露或排放的现象,造成严重的环境污染。石油烃在表层土壤中的积累会导致土壤结构的破坏使土壤通透性能变差,严重影响到农作物的生长和发育。介绍了几种主要的石油污染土壤的修复技术,比较了各类方法的优缺点,重点分析了植物修复石油污染土壤的机理,综述了木本植物、草本植物、花卉植物以及植物联合修复石油污染土壤的应用实例,并对今后植物修复技术的发展方向进行了展望。     

李氏禾研究进展与应用现状

多年生禾本科草本植物李氏禾(Leersia hexandra),起初作为农田杂草备受关注,后因其具有抗旱耐淹耐瘠的生物学特性以及对重金属铬的超富集特性,成为水土保持领域和重金属污染防治领域的研究热点。就李氏禾在土壤重金属污染植物修复上的应用、李氏禾在人工湿地上的应用、李氏禾在水土保持上的应用和李氏禾与农田杂草的控制4个方面进行了综述,并对其今后发展进行展望,以期为该植物的应用提供参考。     

独角莲对城市垃圾渗滤液有机物降解效应研究

[目的]研究植物独角莲对城市垃圾渗滤液中有机物的修复效果。[方法]通过对渗滤液进行不同浓度的稀释和配合化学絮凝剂的处理,检测独角莲对渗滤液的重要有机物衡量指标COD(化学需氧量)、BOD(五日生化需氧量)及NH3-N(氨氮)的降解效应。[结果]独角莲具有在滤液中生长迅速、抗性强和降解效率高的特性,但在100%渗滤液原液(RL)与100%处理后的渗滤液(TL)处理下,由于渗滤液毒性较强,植物在此浓度下的修复效果有限;化学絮凝剂FeCl3处理和独角莲的共同作用可以有效降低较高浓度的渗滤液中的BOD和COD浓度,且TL中的NH3-N含量下降也更显著。[结论]该研究为利用植物处理垃圾渗滤液提供了一个良好的备选材料。     

The economic value of the phytoremediation function – Assessed by the example of cadmium remediation by willow (Salix ssp)

The combination of biomass production with other land use functions in multiple land use systems can reduce biomass production costs if these land use functions generate an economic benefit. Aim of this study is to find and apply methods for the quantification of the economic value of the phytoremediation function (cleaning of the soil by plants). For the purpose the combination of biomass production from willow and the phytoremediation function in a cadmium-contaminated case study area in the Rhine valley (near Freiburg, Germany) was analyzed. Farmers in this area will either have to set the land aside or switch from the high value vegetable production to the production of cereals that generate a lower gross margin. An alternative is the production of heavy metal accumulating willow varieties, which would clean the soil to the cadmium threshold value at which the area can be taken into vegetable production again within a period of six years. Three methods were chosen and applied to quantify the economic value of the phytoremediation function to the farmers: willingness-to-pay, substitution costs, and hedonic pricing. The economic value of the phytoremediation function to farmers as assessed by the substitution cost and hedonic price analysis delivers similar results and is about 14,600 and 14,850 € ha⁻¹, respectively, over a period of 20 years. Farmers, however, are only willing to pay 0–1500 € ha⁻¹, mainly because they consider remediation as the government’s duty. The study shows that the phytoremediation function generates an economic benefit for the farmers, but the amount considered strongly depends on the potential income from the cleaned area, the period of crop production after cleaning the soil and the time needed for cleaning the soil. The application of different methods to assess the economic benefit generates different results; here the use of hedonic price analysis is recommended.     

Selective enrichment of a pyrene degrader population and enhanced pyrene degradation in Bermuda grass rhizosphere

Rhizosphere soil has a more diverse and active microbial community compared to nonvegetated soil. Consequently, the rhizosphere pyrene degrader population (PDP) and pyrene degradation may be enhanced compared to nonvegetated bulk soil (NVB). The objectives of this growth chamber study were to compare (1) Bermuda grass (Cynodon dactylon cv. Guymon) growth in pyrene-contaminated and noncontaminated soils and (2) pyrene degradation and PDP among NVB, Bermuda grass bulk (BB), and Bermuda grass rhizosphere soil (BR). Soils were amended with pyrene at 0 and 500 mg kg^–1, seeded with Bermuda grass, and thinned to two plants per pot 14 days after planting (DAP). Pyrene degradation was evaluated over 63 days. The PDP was enumerated via a most probable number (MPN) procedure at 63 DAP. Bermuda grass root growth was more sensitive to pyrene contamination than shoot growth. Pyrene degradation followed first-order kinetics. Pyrene degradation was significantly greater in BR compared to BB and NVB with rate constants of 0.082, 0.050, and 0.052 day^–1, respectively. The PDPs were 8.01, 7.30, and 6.83 log₁₀ MPN g^–1 dry soil for BR, BB, and NVB, respectively. The largest PDP was in soil with the most rapid pyrene degradation. These results indicate that Bermuda grass can grow in pyrene-contaminated soil and enhance pyrene degradation through a rhizosphere effect.     

植物重金属转运蛋白及其在植物修复中的应用

植物修复技术已成为解决土壤重金属污染的一个绿色环保方法。利用基因工程和分子生物学技术,已经鉴定出一系列与重金属转运相关的蛋白及基因,包括ZIP家族、ABC载体、有机汞裂解酶基因merB、Hg离子还原酶基因merA和金属S蛋白基因MT等。本文着重从细胞、亚细胞水平上综述了一系列重金属转运蛋白的相关分子生物学研究进展及其在植物修复上的应用。     

植物修复对重金属镍污染土壤微生物群落的影响

采用室内盆栽试验方法,研究了外源镍污染土壤的植物修复对土壤微生物群落的影响。试验用水稻土中添加NiSO4.6H2O(100~1 600 mg kg-1)经过12周的驯化培养后,种植了2种超累积植物和1种耐性植物,经110 d的试验后进行了植物修复后土壤微生物活性的分析。结果表明,非根区土中添加镍的质量分数为100 mg kg-1时,对土壤中细菌、真菌和放线菌总数有一定的促进作用,土壤中微生物生物量最大;当添加镍的质量分数大于100 mg kg-1时,将对土壤微生物群落造成不利的影响。在植物修复过程中,通过植物的减毒(吸收重金属)作用和根系分泌物的作用,改善了土壤微生物的生存环境,提高了土壤微生物的数量和生物量。经过植物修复后,根区土壤微生物较非根区土壤的丰富,土壤微生物群落总DNA序列多样性指数相应增加,但不同植物对根区土壤微生物的贡献是不同的。     

土壤重金属污染的植物修复与金属超富集植物及其遗传工程研究

本文综述了土壤重金属污染的植物修复、金属超富集植物及其遗传工程的最新研究进展及存在问题,并提出加紧筛选和发现野生高生物量的金属超富集植物,在现有高生物量作物种质资源中筛选金属超富集作物,应用遗传工程技术把野生植物的超富集基因转移到现有高生物量植物(作物)中,寻找综合、可持续的植物修复手段等对策。     

马唐对Pb污染土壤的修复作用

研究了农田杂草马唐(Digitaria sanguinaisl)对于Pb污染土壤的修复效果。通过45d的盆栽试验研究观测了马唐在Pb污染下的生长情况和富集能力、土壤重金属Pb浓度与土壤酶活性的关系,以及经马唐修复后土壤酶活性恢复情况。结果表明:Pb污染对马唐的生长有明显的抑制作用;五种土壤酶活性均随土壤Pb浓度的增加而降低,回归分析表明土壤过氧化氢酶和脲酶活性与土壤Pb浓度极显著相关,可表示出土壤受Pb污染程度;Pb污染土壤经过马唐修复后,过氧化氢酶和脲酶活性得到恢复,可根据它们的活性恢复状况判断马唐的修复效果。     

Phytoremediation of selenium‐contaminated soils: the efficiency of different cropping systems

Field experiments were conducted at two locations in the seleniferous region of northwestern India from 2001 to 2006 to evaluate the efficiency of four cropping systems in removing Se from contaminated soil containing 2843–4345 μg Se per kg in the surface layer (0–15 cm). Rapeseed (Brassica napus) followed by arhar (Cajanus cajan), sunn hemp (Crotalaria juncea) or cotton (Gossypium arboretum) and wheat (Triticum aestivum) followed by rice (Oryza sativa) were the four cropping systems. The total biomass generated by Brassica‐based systems ranged from 16 to 21 t/ha when harvested at maturity. Corresponding values for a wheat–rice sequence were 22–26 t/ha. Among the different crops at both the experimental sites, the highest Se content was recorded in leaves (157–209 mg/kg), grains (64–201 mg/kg) and stems (42–93 mg/kg) of Brassica and the lowest in the shoots (10–27 mg/kg), grains (5–13 mg/kg) and straw (13–20 mg/kg) of the rice crop. Except for S and P, concentrations of other nutrients (Zn, Cu, Mn and Fe) were not significantly affected by variations in the Se content of plants. Significant correlation coefficients were observed between Se and S (r = 0.838, P ≤ 0.001), Se and P (r = 0.817, P ≤ 0.001) at the peak flowering stage (n = 16), and r = 0.743, P ≤ 0.001 and r = 0.498, P ≤ 0.05, respectively, at the maturity stage (n = 16). Total Se removal through harvested biomass of rapeseed‐based cropping sequences varied from 716 to 1374 g/ha/yr at peak flowering and 736–949 g/ha/yr at the maturity stage. Corresponding values for a wheat–rice system were 435–492 and 370–517 g/ha/yr, respectively. The amount of Se recycled through leaf senescence ranged from 255 to 500 g/ha/yr for Brassica‐based cropping systems. In the wheat–rice system, Se addition through irrigation varied from 170 to 243 g/ha/yr and was three to four times more than that added in Brassica‐based systems. On completion of the phytoremediation experiments at site I, Se removal through harvested biomass at maturity was 1.7–5.1% of total Se in the soil down to a depth of 120 cm and 4.8–13.2% at site II. Analysis showed that Se losses under different crop rotations were 18.5–24.5% at site I and 21–33% at site II of total soil Se. Thus, at both sites 16–20% of total Se lost from the soil was unexplained. Results show that Brassica‐based cropping systems lead to significant reductions in Se capital of contaminated soil over 2–3 years. Although a long‐term commitment is required, adoption of Brassica‐based systems as a regular agricultural practice must lead to sustainable management of seleniferous soils.